1. Field of the Invention
This invention relates to operating handles for electrical switches or circuit breakers mounted within an enclosure, and more particularly to operating handles mounted on the door of the enclosure and providing an interlock to prevent opening of the door when the switch or circuit breaker is turned on.
2. Background of the Invention
Manually operated electric circuit breakers are usually mounted inside an enclosure as a safety measure. Operation of the circuit breaker is accomplished by use of a handle operated from outside of the enclosure when the enclosure is closed. A handle may be simply an extension of a shaft passing through a hole in the enclosure, or the handle may be a more complex mechanical arrangement which is mounted on the exterior of the enclosure and engages a shaft protruding through a hole in the enclosure. An additional function provided by the operating handle is to interlock the door of the enclosure in order to prevent opening of the door while the circuit breaker is turned "on".
Present devices designed to accomplish both operation of the circuit breaker and interlocking of the door use the position of the handle to release the interlock. When the handle is in the position corresponding to the circuit breaker being "off" it is common practice for a pin, or its equivalent, to align with a slot thereby releasing the door. Apparatus having this type of interlock is shown in U.S. Pat. Nos. 3,657,497, 3,335,238, 3,226,500, 2,806,099, and 2,698,361.
A problem with devices of the past is that the mechanical alignment required by the two processes, moving the circuit breaker into the "off" condition and simultaneously aligning a pin for release of the door is not always met at the same lever position. Manufacturing tolerances and alignment of parts within the enclosure lead to a lack of alignment which prevents simultaneously achieving the two processes. For example, the door may release without the circuit breaker toggle being moved far enough to drive the circuit breaker into the "off" condition.